1. Field of the Invention
The present invention relates in general to core samples removed from soft formations or loosely consolidated and unconsolidated areas or portions of the earth. More particularly, the present invention relates to methods for mounting or confining poorly consolidated and/or unconsolidated core samples for subsequent handling and testing.
2. Description of the Prior Art
It is generally the practice when drilling oil and gas wells to recover whole vertical sections of prospective geological formations at various depths in the drilling operation. This routine sampling is called coring and aids in determining the geological characteristics of the sub-structure. It is also often necessary to core drill and obtain cores of materials at construction projects and the like, as where the nature of the overburden above bedrock is to be ascertained.
In the majority of cases, the core material obtained from the core drillings is sent to a laboratory for testing. The accuracy of the analysis and testing is inversely proportional to the degree to which the integrity of the core sample is disturbed or changed as the core sample is removed from the earth, transported to the laboratory and handled at the laboratory during the testing thereof. As would be expected, greater care is needed in the handling of poorly and/or unconsolidated core samples than with consolidated core samples. Many of the prior art devices are directed to the removal of core samples from the earth. For example, U.S. Pat. No. 4,071,099 discloses a housing for receiving a conventional rubber sleeved core sample from a vertically suspended core barrel. The housing is adapted for the circulation therearound of a subfreezing mass for the freezing and solidification of the core fluids contained therethrough. Also disclosed is an elongated housing adapted for the receipt of the core while within the rubber sleeve and including means for introducing a casting medium substantially around and longitudinally along the core. Means are included for shielding an arcuate longitudinal portion of the core from the casting medium to facilitate access to the partially encased core.
U.S. Pat. No. 4,156,469 discloses a drilling system for obtaining cores of unconsolidated material by using an apparatus which permits the core barrel to remain stationary while the auger rotates. The apparatus further includes means for fitting a friction reducing sleeve of woven nylon about the core as the drilling occurs and thus permit the core to freely slide upwardly into the core barrel within the sleeve.
U.S. Pat. No. 4,371,045 discloses apparatus for removing unstable cores from the earth which includes apparatus operatively connected to the top of the drill pipe which allows the core barrel to be positioned within a chilling vessel and a cryogenic fluid to flow through the chilling vessel to stabilize the core sample before the core barrel is removed from the top of the drill pipe.
The present invention as claimed is intended to provide a solution to various prior art deficiencies which include mountings which are not suitable for allowing resistivity measurements on the poorly consolidated or unconsolidated core samples. Prior art mountings do not provide adequate viewing of the core sample to allow detection of cracks or other textural anomalies in the core sample. Some prior art mountings do not provide adequate confinement of the core sample to adequately assure the physical integrity of the core samples during handling and testing and thereby do not minimize alteration of the characteristics of the physical structure of the core sample.